The present invention relates to an air cleaner for an internal combustion engine.
Japanese Laid-Open Patent Publication No. 11-343939 discloses an air intake duct for an internal combustion engine that is formed through compression molding of nonwoven fabric containing thermoplastic resin binder. The walls of the air intake duct disclosed in the publication have a certain degree of air permeability. Accordingly, a part of sound waves of intake noise goes through the duct walls. This suppresses generation of standing waves of the intake noise and reduces intake noise.
In the engine compartment of a vehicle, many parts other than the air intake duct are installed. Accordingly, for some types of vehicles, it may be difficult to accommodate the length of the air intake duct due to space limitations within the engine compartment. In such a case, even if the air intake duct as disclosed in the above publication is employed, it is almost impossible to absorb sound waves through the duct walls, so that the reduction of intake noise would be difficult.
It is an objective of the present invention to provide an air cleaner for an internal combustion engine that reduces intake noise while preventing an increase of its size.